Finally had a chance to investigate the latest broken motor mount. Same bracket sheared again:

I decided to go ahead and unbolt the rear bobble strut and the front torque strut, but imagine my surprise when I found:

That's the bobble relocation bracket sheared off at the bend. Because this chassis was originally an ATX, the k-member has no provision for mounting the bobble strut that the MTX uses. There's a guy who makes (made?) A bracket that bolts to the top of the K, under the power steering rack that the bobble can then attach to. Well, mine is busted.

I thought about getting a new one but then I remembered that I've got a welder and what do I have to lose by trying to fix it.

The plate was a little bent, so I put it under the press to flatten it out.

After grinding off the paint, I put a bevel on each part so it would go together. Magnets held it together while I laid a bead on the outside and then on the inside:

By the time I had that done it was all really got and I was tired so I'll save the re-installation until another night. The biggest part of this, though, is just that I'm actually doing something.

I'm not sure what I'm going to do at this point. I'm thinking about getting a 2nd gen side mount that bolts up to the strut tower.

Saturday? Did I calendar fail? I thought the last event of the season was last weekend. Sounds like that doesn't matter though.

To answer the question, though, I should have it back together tomorrow actually. My real question is what broke when and cause what else to fail? Did the bobble mount fail and cause the motor to move which caused the side mount to fail? Or did the side mount failing break the bobble mount? Did it break the first time the side mount failed? Who are you? Are we enemies? Why am I on this wall? Where is Buttercup?

How is the trans mount? If it failed the power train can move a lot. Smashing the other mounts.

I guess check for preload. Allow some dampened movement. I recall someone on neons.org planning to use a timing belt tensioner pulley and the timing belt tensioner cylinder to cobble a dampened mount. Never saw it come to reality though.

That would probably never work. Hydraulic tensioners really don't like to be moved very much, and you can actually damage them by compressing them too fast. If you do it right it should take about two minutes to compress one.

The trans mount seems(?) to be okay, but I'll poke around in there and investigate further. That mount is a stiffened mount, but not solid, and I do have extra mounts around and some prothane inserts I could put in there if it's busted.

All the mounts are reinstalled at this point and I'm ready to give it some testing. I have the motor canted back a little bit more than it was before and everything is pretty solid - it will move, but not easily. The bobble bracket is welded back up and I left a little bit of looseness in it such that the bottom pivot will rotate instead of being super tight. The trans mount seems fine - I didn't pull it out, but I got in there with a light and a mirror and I don't see any breakage. There are some areas where I could add a front mount on the bottom, but the heim joints I bought are M9 sized somehow and the bolts that would need to run through it are either m10 or m12. I'm going to try to take it for a drive tonight and see how much movement I get.

When I don't drive this car for a while, my memories of it shift and alter in odd ways such that I remember the sounds, I remember the sudden loss of power and the car dying on the course, but I forget the feel of the front wheels trying to rip the chassis in half as it explodes away from a stop sign. Last night, I put the street tires back on, warmed it up, and took it for a short drive through the neighborhood. Everything checked out (and I discovered that they've built an absolute butt-load of houses in the back section of the subdivision) so I ventured out onto the main road to see how things were holding together. I still have way more power than tire, but everything is running really well, despite the motor flopping about from time to time.

One minor problem came up as I was driving -- the car started running on 3 cylinders for a little while. I noticed that it was doing that at the last rallycross, before the mount sheared on me, but like then, before I could get it to a spot where I could investigate, the problem resolved itself and everything was fine. I suspect there's a loose plug wire or a loose injector wire, but that's something I'm going to have to try to troubleshoot while it's happening. In the meantime, I disconnected and reconnected all the plug and injector wires just to be sure, but I'll keep an eye out for it. I don't think it's really a big problem.

Another thing I need to keep an eye on is the transmission. There's some fluid leaking from it and I'm not 100% sure where it's coming from. Initially, my thought was that it was an axle seal, but those have been replaced multiple times. Currently, my working theory is that when I opened it up to install the OBX LSD, I didn't do a good enough job with the anerobic sealant and it's leaking from the case. For now, I'm just going to keep it topped up, but long-term planning involves a good de-greasing and pressure washing and then letting it sit for a week to find the source.

The only other thing I need to do this week is to dump half the water out of the radiator and top it off with some antifreeze. Temps are scheduled to drop below freezing overnight later this week and while the garage will probably be okay, there's no need to chance it.

Pondering the broken bobble mount bracket, I'm thinking that maybe the bracket snapped because the engine was bending the angle up then pushing it back, and repeating that process over and over which caused it to break there. I can't really put a gusset into the bracket because of the K-member, but I suspect I need to come up with some sort of solution there to keep it from happening again. This is a time where it would be really helpful to know what broke first -- if that failed and then caused the side mount to go, fixing that and keeping an eye on it should be the way to go, but if the side mount failed and caused the bobble bracket to break, then I may just be right back at the beginning again which is not cool.

Yes, I'm one of those guys that doesn't update for two months and then all of a sudden it's five posts a day.

I had to winterize the motorhome today, so I took the beast over there, picking up antifreeze on the way. I'll get to that tomorrow night probably. For this discussion, my scale goes like this:

<grandma>-------<normal>-------<spirited>-------<OMFGWTFBBQ>

As long as I keep throttle application under OMFGWTFBBQ, everything is fine. Boosts right up to 15psi, sounds good, pulls strong, no problems. I can even go WOT without causing anything untoward from happening as long as I'm pulling from, say, 35mph to 50mph in 5th gear. If, on the other hand, I go full OMFGWTFBBQ mode on it, things get weird. As I type this, I'm starting to think that the main difference is bouncing it off the rev limiter versus not, but basically it will pull hard, break the tires loose, make great noises, and then run on three for a while before returning to normal. At least I can reproduce it fairly reliably. The other common thing is that it also triggers the knock sensor (which I believe is way too sensitive), so it could be something that either knock retard or the rev limiter is doing causes a marginal component to misbehave.

Two things today: The power steering fluid was way low, so I topped that off. Many fewer noises are made now by the pump, and that's gotta be a good thing. It was only low because I had the hoses off to swap motor mounts and forgot to re-fill the reservoir, so nothing wrong with the system, which is good.

I also played a bit with the uncommanded cylinder deactivation system that seems to have manifested upon the car. I'm noticing that I can cause the problem by wailing on the throttle pedal, spinning the wheels, and triggering the knock sensor. It drives with a massive miss on one cylinder for a while and then fixes itself, but it comes back gradually. By that I mean that right away it's full-on sputtering for a while, then the sputter just gradually smooths out until it's running on all four again. My best guess right now is that it's either a fuel delivery problem or I have managed to destroy something inside the engine in a really weird way. Some night this week I'm going to swap out the injectors to see if that has any effect.

Swapped out the injectors this morning and no difference. That's the bad news. The good news is that I believe I have collected enough data to have an even better hypothesis! I think I may have inadvertently set the recovery time on knock detection to something like 15-20 seconds and I know the knock sensor is a little too sensitive right now. When I get home tonight, I'll plug in the laptop and check it out.

Back in November, I thought I had squared this away -- I turned down the knock sensor a bit and the misfiring stopped. I put a few hundred trouble-free miles on the car over the winter and all seemed to be good.

The last time I had the car out, though, I wasn't driving it very hard but it suddenly started running on only 3 cylinders. Waiting for the weather to warm up and other projects to get completed, I didn't have a chance to do much about it until today. By unplugging injectors, I can confirm that it's cylinder #3 at fault. The O2 is telling me that it's running rich, not lean, so I didn't think the injector would be at fault, but I swapped it out anyway. Same result.

Next thing to check will be spark and I plan to do that tonight along with checking compression to see if I've blown up something serious. 43 days until Points Event #1, so this is going to have to take precedence over working on the Miata.

Back in November, I thought I had squared this away -- I turned down the knock sensor a bit and the misfiring stopped. I put a few hundred trouble-free miles on the car over the winter and all seemed to be good.

The last time I had the car out, though, I wasn't driving it very hard but it suddenly started running on only 3 cylinders. Waiting for the weather to warm up and other projects to get completed, I didn't have a chance to do much about it until today. By unplugging injectors, I can confirm that it's cylinder #3 at fault. The O2 is telling me that it's running rich, not lean, so I didn't think the injector would be at fault, but I swapped it out anyway. Same result.

Next thing to check will be spark and I plan to do that tonight along with checking compression to see if I've blown up something serious. 43 days until Points Event #1, so this is going to have to take precedence over working on the Miata.

Back in November, I thought I had squared this away -- I turned down the knock sensor a bit and the misfiring stopped. I put a few hundred trouble-free miles on the car over the winter and all seemed to be good.

The last time I had the car out, though, I wasn't driving it very hard but it suddenly started running on only 3 cylinders. Waiting for the weather to warm up and other projects to get completed, I didn't have a chance to do much about it until today. By unplugging injectors, I can confirm that it's cylinder #3 at fault. The O2 is telling me that it's running rich, not lean, so I didn't think the injector would be at fault, but I swapped it out anyway. Same result.

Next thing to check will be spark and I plan to do that tonight along with checking compression to see if I've blown up something serious. 43 days until Points Event #1, so this is going to have to take precedence over working on the Miata.

If you need any help or parts I have a big hoard of parts and cars.

It was your thread that actually reminded me that it was a nice day out and I needed to go try swapping that injector! (Actually, I was hoping that it healed itself over the last couple weeks, if we're being honest here...)

I have strongly considered getting an interior for the car again -- I sold off all the plastic trim and such back when I was originally making this a Challenge car. If you happen to have a two-door parts car with decent interior bits (headliner, pillar trim, door cards, door scuff plates, big plastic panels in the rear, and maybe even a rear seat...) I might be interested, once I get this issue figured out and resolved. Heck, I've even toyed with the idea of re-bodying the thing into something that didn't have a tweak and a rebuilt title, but I don't think there are any more good body/ruined drivetrain Neons left for cheap anymore.

My first stop on the journey was to pull the plug and test spark, so I took my folding worktable out into the driveway and arranged my tools and coffee. In addition to the standard things, I brought my remote starter switch, compression tester, and the spark tester thing. Things didn't get very far past step #1 because when I removed the spark plug in #3, it looked like this:

No wonder the cylinder isn't firing -- there's absolutely no way to get a spark when the thing is touching. Why is it touching, though? That's the real question -- in "theory" the piston shouldn't ever get that high. Also of note, the plug was wet when I pulled it out, but after a minute in the fresh air, it was totally dry so no oil on it, just copious amounts of gasoline. A probe inserted into the plug hole confirmed that the piston was going up and down as it should when the crank rotated, so nothing broken there. Next step was to check compression to see how bad things were on that front. I had to do this cold, of course, but still:

I'll take 140psi as an indicator that nothing is terribly amiss in the cylinder.

Using a pliers, I re-gapped the plug, put a little grease on the end, put it back in, turned the motor over and pulled it back. Grease was undisturbed, so I cleaned it up, put it in, hooked everything back up and started her up. Everything is just fine. No weird noises from the stethoscope, O2 gauges read normal, vacuum is good, and it revs great and pulls hard. So, symptom solved (yay!), but I'm a little hesitant to call it officially fixed because I don't have a true cause of why that plug got bent up. Perhaps I over-revved it a bit and got a little stretch from the rod? I'm thinking that maybe a very slightly shorter plug might be in order, but I may just double-check and turn down the rev limiter -- it's not making any power way up there anyway, so all I'm really doing is breaking things. More likely, I'm seeing a symptom of detonation and I need to turn the knock sensor back up a bit. I think it just might be time to get this thing on a dyno with someone who knows something about Megasquirt and do a little actual tuning.

Glad nothing seems permanently damaged. My memory is a little foggy, but there do seem to be a lot more threads on that spark plug than I remember mine having. You do have a different cylinder head, though.

Yeah, the 2.4T head has more reach on the plugs than the 2.0 or the N/A 2.4 does. 20-someodd mm versus 16 or 19 or something like that. When I unboxed them originally, I was a bit apprehensive until I compared them against the ones that were in there when we pulled it at the junkyard.

Yeah, the 2.4T head has more reach on the plugs than the 2.0 or the N/A 2.4 does. 20-someodd mm versus 16 or 19 or something like that. When I unboxed them originally, I was a bit apprehensive until I compared them against the ones that were in there when we pulled it at the junkyard.

Just had another thought regarding this. Are the pistons in the PT Turbo the same as the pistons in the SRT-4? Didn’t you switch to SRT-4 guts when you did the rebuild? Is it possible there’s a smidge less clearance? Also, did you use a factory style head gasket, or something potentially thinner? Just trying to think of any possible reason the spark plug would get hit. The 2.4 is non interference, and I’d think compression is low enough that there is no logical reason for the plugs and the piston to ever meet.

The SRT4, PTGT, and PT Turbo-lite are all the same motor and I used all the parts that were originally in the turbo-lite when I rebuilt it. I can't imagine a scenario where something could come so loose as to cause the piston to impact the plug and then just go back to normal.

Filling the cylinder with fuel isn't entirely outside the realm of possibility. I've got a different injector in there now, so if that was the problem, it shouldn't come back.

I'm not adverse to adding some heat sheilding for the coil pack. I think modern had something like that at one time, but I've got some aluminum that I could bend and cut that would get the job done.